Circuit breaker with magnetic trip adjusting means



R. E. FALK April 27, 1965 CIRCUIT BREAKER WITH MAGNETIC TRIP ADJUSTINGMEANS Filed Feb. 19, 1963 2 Sheets-Sheet. 1

Il-rll April 1965 R. E. FALK 3,181,041

CIRCUIT BREAKER. WITH MAGNETIC TRIP ADJUSTING MEANS Filed Feb. 19, 19632 Sheets-Sheet 2 INVENTOR. RONALD E. 51 LA,

ATTORNEY.

United States Patent M Ronald E. Falls, Bristol, Conn, assignor toGeneral Electric Company, a corporation of New York Filed Feb. 19, 1963,Ser. No. 259,674

6 Claims. (Cl. 317--ll76) My invention relates to electric circuits, andparticularly to electric circuit breakers which include adjustablemagnetically operated means for causing automatic opening or tripping.

in accordance with the prior art, electric circuit breakers of the typedescribed have been provided with adjustable magnetic tripping meansincluding an adjusting member having a limited amount of movement, whichthe user can adjust to vary the tripping point of the circuit breakerbetween'certain predetermined limits. Thus, for example, at one settingof such a users adjusting knob, the circuit breaker may trip at timesits normal currentcarrying' rating (designated at 5 X). At the oppositelimit of the movement of the users adjusting knob, the same circuitbreaker may trip magnetically at 12X.

Also, in accordance with the prior art, such circuit breakers have beenprovided with means which is adjustable at the factory, whereby not onlythe starting point, but also the span of the range of adjustmentachieved by the users adjusting knob may be varied. More particularly,with such adjusting mechanism,-although the permitted range of movementof the users adjusting knob remains constant, the high and low trippingpoints brought about by such movement can be set, independently of eachother, by the manufacturer. Circuit breakers having adjusting mechanismsof this type are shown and claimed, for example, in prior applicationSerial No. 62,184, Klein and Powell, filed October 12, 1960, now PatentNo. 3,084,23 6, issued April 2, 1963, and in Patent No. 3,053,954,Jencks and Murphy, issued September 11, 1962, both assigned to the sameassignee as the present invention. 7 s In each of the aforesaidinventions, the users adjusting knob is fixedly attached to an adjustingmember which is rotatably carried in the housing, the knob being mountedafter the factory adjustment of the parts has been carried out. In orderto provide an inexpensive non-rotatable mounting of this knob, and oneWhich'can be quickly assembled, it has been the practice to useinterengaging flutes and ribs, or a flat-sided or non-circular shaft onwhich the knob is mounted. With such arrangements, the indicating knobcannot always be placed such that it points exactly to the high or lowsetting inscribed on the circuit breaker casing, since there are only anumber of particular positions in which it may be mounted. Thus, forexample, if an arrangement is used including teeth and correspondingnotches 18 in number, the placement of the knob could involve a possibleerror of degrees. Some error, of course, would also apply to allintermediate settings.

In addition, in accordance with the prior designs, the factoryadjustment has required adjustment. of certain parts which are notreadily accessible, thus adding to the difficulty and slowing down theadjusting process.

It is an object of the present invention to provide a magnetic adjustingmechanism for adjusting the magnetic tripping point of an electriccircuit breaker of the type described which permits positioning of theindicating knob to exactly correspond with the markings carried by thecircuit breaker casing so that no substantial error is indicated eitherat the beginning or end, of adjustment or any point intermediate thesesettings.

It'is another object of the inventionto provide an elec- 3,131,941Patented Apr. 27, 1955 tric circuit breaker including an adjustablemagnetic tripping means of the type described in which the initial orfactory adjustment can be more readily accomplished.

In accordance with the invention in one form, an electric circuitbreaker is provided including a member movable to initiate automaticopening of the circuit breaker, and a magnetic solenoid including anarmature which is movable to engage the aforesaid tripping member uponthe occurrence of predetermined current conditions. Means is providedfor adjusting the tripping point of the solenoid including a pivotallysupported cam follower whose position is adjusted by rotating a cammember between predetermined limits. The cam follower member ias oneposition in which its working surface extends in a direction parallel tothe axis of rotation of the cam member which works upon it. An initialadjustment is made in this setting to determine one end point of theoperation of the solenoid. The cam member is also movable in a directionparallel to its own axis, to move it toward or away from the pivot ofthe cam follower member, and thereby to vary the mechanical advantage ofthe carnmember on the cam follower. Such motion, however, does notchange the position of the cam follower member when the parts arereturned to their original condition in which the cam follower surfaceextends parallel to the axis of movement of the cam member. The twosteps of adjustment, therefore, are (l) to set the parts so that the camfollower member surface is parallel to the axis of the cam member andthen to adjust a characteristic of the solenoid, such as its gapsetting; and (2) then to adjust the cam member in a direction parallelto its own axis to vary the mechanical advantage, until it is such as togive the desired amount of movement when the cam member is rotated toits opposite position.

In accordance with the invention, the cam member is supported on athreaded shaft which in turn extends through a bushing and has its upperend accessible to carry the users adjusting knob. Rotation of thethreaded bushing member moves the cam shaft upwardly or downwardly, theend thereof sliding within the users adjusting knob. Initial adjustmentmay therefore be accomplished by simply holding the users adjusting knobfrom rotating in the high or low position, and then rotating theadjusting bushing to move the cam member to the desired verticalposition.

In accordance with another aspect of the invention, the threaded bushingreferred to is itself thrcadedly carried by asupporting member by areverse-direction thread so that rotation thereof causes verticalmovement of the cam member equal to the sum of the pitches of thethreads of p the cam shaft and the bushing member.

The invention will be more fully understood from the following detaileddescription, and its scope will be pointed out in the appended claims.

In the drawings,

FIGURE 1 is a side elevation view of a position of the circuit breakerincorporating the present invention, a portion of the side wall beingbroken awa FIGURE 2 is an elevation view of the tripping mechanism ofFIGURE 1 takensubstantially on the line 22 of FEGURE l;

FIGURE 3 is a fragmentary view of a portion of the casing of the circuitbreaker of FIGURE 1 showing the users adjusting knob;

FIGURE 4 is a plan view of the adjusting cam of the mechanism of FIGURE1, and

FIGURE 5 is an elevation view of the cam and cam follower member.

I in the drawings, the invention is shown as incorporated in an electriccircuit breaker including a molded insulating casing having a base it!and a cover 11. The

circuit breaker shown is of the three pole variety andincludes threepairs of relatively movable contacts, not shown, and manually operableoperating mechanism, not shown, adapted to be actuated by the handlemember 12 for moving all three sets of contacts simultaneously betweenopen and closed circuit positions.

The operating mechanism includes a releasable member 13 which isnormally held by an intermediate latch member I4 pivotally supported inthe casing on a pivot pin 15. The intermediate latch member 14 has acentral cutout portion 16 into which a primary latch member 17 extendsso that it engages a portion of the latch member lid and preventscounterclockwise rotation thereof as viewed. The primary latch 17 isrigidly carried by a common trip bar 18 extending across all three polesof the circuit breaker and having extensions 19 adapted to be engaged bythe tripping mechanism in a manner to be described. Rotation of the tripbar 18 in a clockwise direction by the tripping mechanism causes releaseof the intermediate latch member 14 and therefore release of thereleasable member 13, and automatic opening of the contacts of thecircuit breaker.

For the purpose of causing releasing movement of the trip bar 18 inresponse to predetermined current conditions through any one of thepoles of the circuit breaker, current-responsive tripping mechanism isprovided at each pole of the circuit breaker. Since the trippingmechanism in each pole is substantially identical, the mechanism of onepole only will be described. The tripping mechanism includes a metallicframe member 2t) which is in the form of a plate, having portionsthereof bent over or bent out connected to the frame member 20 andthence to the terminal member 22. The other end 31 of the winding 29 isconnected to the movable contact of the corresponding pole of thecircuit breaker, not shown. The armature member'Zti carries an operatingextension 32 attached thereto by suitable means such as by screws orrivets 33. The extension 32 is insulated from the armature 28 bysuitable means such as insulating sheet 32A, the screw 33 beinginsulatedfrom the extension 32 by insulating washer 32B. The extension 32 carriesan operating screw 32 which is adapted to engage the extension 19 of thetrip bar 13 when the armature 28 is attracted to the pole piece 27.

The travel of the armature 28 in the opening direction is limited byengagement with a calibrating screw 36 at the outer end of the extension32. The calibrating screw 36 is carried by an integral offset portion 37of the frame member 20. The armature member 28 isibiased constantlytoward open or unoperated position by means of a tension spring 38 whichhas one end connected to a stud-39 carried by the extension 32 and hasits other end carried by an end portion 4b of a pivotally supported camfollower, member 41 pivotally supported on the frame 2% by pivot pin 42(see FIGURE 2). I

For the purpose of adjustably positioning the cam follow member 41,adjusting means is provided including a rotatable cam member 43rigidlyattached to the end of a threaded cam shaft 44. The cam shaft 44 isthreadedly engaged in the bore of an adjustable sleeve member 45 havinga non-circular head portion 46. The upper end portion 44A of the shaft44, which .is non-threaded, is also made non-circular, as shown forexample in FIGURE 4.

The sleeve member 45 is threadedly engaged at two points in a generallyC-shaped bracket 48 rigidly attached to the frame member 2d. The bracket48 includes an integral downwardly projecting extension 49 having a slot50 therein which is disposed and arranged to slidably receive the righthand portion 51 of the cam follower member 41.

The end portion 44A of the shaft 44 is slidably received Within acorrespondingly shaped blind hole 51A in the insulating knob 51. Theinsulating knob 51 is provided to enable the customer or user to adjustthe tripping point of the breaker within a predetermined range, in amanner to be described. The knob 51 projects through an opening 52 inthe top wall of the casing cover 11. The knob 51 which is slidable onthe shaft portion 44A, is biased upwardly by a compression spring 53surrounding the portion 44A of the shaft 44, which presses the flangeportion 513 of the knob 51 against the inner surface of the top wall ofthe casing.

The cam follower member 41 has a linear cam follower surface 41A. Thecam follower 41 is constantly biased in a counterclockwise directionagainst the cam 43 by a tension spring 54 having one end portionconnected to the extension 413 of the member 41 and having its other endanchored to a bent-over portion 55 of the frame 20.

As shown in FIGURE 3, the portion of the users adjusting knob 51 whichprojects through the opening 52 of the cover 11 is provided with asuitable indicator such as the arrow 51C, see FIGURE 3, and the casingcover Ill has a series of graduations marked off around the hole 52between extreme positions designated as L0 and iHII H Operation headjustment or calibration of the circuit breaker in accordance with theinvention may, for example, be carried out as follows. The usersadjusting knob 51 is turned to the HI position. In this position, thearrow 51C will point to the indicator HI, and the cam 43 will be in theposition which permits the cam follower member 41 to rotate to its mostcounterclockwise position under the influence of'the tension spring 54,i.e., the position in which the surface 41A is closest to the shaft 44.Rotation of the cam member 4-3 in the HI direction is limited by thestop portion 43A of the cam member 43 as shown in FIGURE 4.

With the parts in this condition, the spring 38 will be elongated itsmaximum amount. In this connection, it

should be noted that the spring, 54 is made substantially stronger thanthe spring 38, so that the cam follower member 41 is always held againstthe surface of the cam member 43 at all times.

Since in the HI position being discussed, the spring 38 is elongated itsmaximum amount, there will be a maximum'hold-open bias exerted on thearmature 28, through the extension 32, by the spring 38. A relativelyhigh amount of current will therefore be necessary to cause tripping.With the .cam member and the cam follower in this position, thecalibrating screw 36 is adjusted to vary the air gap of the magnet orsolenoid 25 until tripping occurs at the exact value desired for the HIsetting of the users adjusting knob.

After this has been accomplished, the users adjusting knob is rotated tothe LO position. In the LO position, the cam follower member 4-11 isforced'away from the shaft 44 to its most clockwise position. Thisrelaxes or; shortens the tension spring 38, decreasing the holdopen biason the armature. It will be noted, however, that the magnet air gapremains constant, since the extension 32 is still held against thecalibrating spring 36.

i The breaker is then tested to discover at what value tripping occursin this setting. If it is found that tripping occurs at too high avalue, this would indicate that a lesser hold-open bias is needed. Adecrease in the bias is provided, without changing the position of theusers adjusting knob, by lowering the vertical position of the cammember 43, moving it toward the pivot '42 of the cam follower member 41,as indicated in dotted lines in (:3 FIGURE 5. This raises the end 4% ofthe member 41, allowing the spring 38 to shorten.

If, on the other hand, it found tripping occurs at too low a value, thecam member 43 is moved upwardly vertically, thereby moving it away fromthe pivot 42 and allowing the member 41 to move slightly further in thecounterclockwise direction under the bias of spring 54, and furtherelongating the spring 38.

In accordance with the invention, the vertical movement of the cammember 43 is accomplished without rotational movement, by manuallyholding the users adjusting knob 51 from turning, While the threadedsleeve member 46 is turned in one direction or the other. Since theshaft 44 is threaded in the bore of the sleeve 44, such rotation alonewould cause vertical movement of the shaft 44 so long as the sleeve 45is restrained from vertical movement.

In order to provide a greater amount of movement of the shaft 44 for agiven amount of rotation of the sleeve 45, however, the sleeve 45 isitself threadeoly sup ported in the bracket 48. The thread of the sleeve45 in the bracket 43, i.e., the external thread on the sleeve 45, ismade to run in one direction, such as a right-hand thread. The thread ofthe shaft 44 in the sleeve 45, i.e., the internal thread of the sleeve45, is made to run in the opposite direction, such as a left-handthread. Thus the sleeve member as is rotated so as to thread downwardlyas viewed in Fi'GURE 2, the shaft 44, which is being held from rotationwith respect to the sleeve 46, is also projected downwardly with respectto the sleeve 45. so

that the total downward movement of the cam member is equal to the sumof the threading movements of both the sleeve 45 and the shaft 44. Thispermits a substantial movement of the cam member 43 without acorrespondingly great movement of the sleeve 45, so that a relativelysmall amount of adjusting movement is necessary. In practice, forexample, is has been found that in a circuit breaker of the typeillustrated, less than a full turn of the sleeve 45 is ordinarilyrequired.

it will be appreciated that, if desired, other means for achieving thevertical adjustment of the cam member 43 without rotation may beutilized, such, for example, as that shown in the aforementionedapplication Serial No. 62,184.

It is a particular advantage of the applicants present invention thatthe cam member 43 can be restrained from rotation during the initialadjusting stage by simply holding the users adjusting knob fromrotation.

It will also be observed that while the vertical position of the cammember 43 is varied, the position of the users adjusting knob, withrespect to the casing cover 11, remains unchanged, since it isconstantly biased against the underside of the cover by the compressionspring 53, while the upper end 44A of the shaft 44 moves slidably withinthe hole 51A. The required adjustment of the tripping point at the lowsetting can therefore be achieved while the cam and the users adjustingknob are held exactly in the LO position as marked on the circuitbreaker casing while the cam member 43 is being varied in its verticalposition. Similar adjustment is possible in the Hi position. Thus exactconformance of the end points of the adjustment with the high and lowmarkings on the circuit breaker casing is assured.

While the invention has been shown in only one specific embodiment, itwill be readily apparent that many modification thereof can be made, andI therefore intend by the appended claims to cover all suchmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is: V

1. An electric control device including:

(a) an enclosure,

(b) a cam follower member pivotally supported in said enclosure andincluding a cam follower surface,

(0) means operably connected to said cam follower member for varying thesensitivity of said device,

(d) an elongated cam shaft, 1

(e) a generally tubular supporting sleeve supporting said cam shaft insaid enclosure,

(i) said supporting sleeve being rotatable while said cam shaft isrestrained from rotation to cause longitudinal shifting of said camshaft with respect to said enclosure,

(g) a cam member carried by said cam shaft adjacent one end thereof anddisposed and arranged to engage said cam follower surface of said camfollower memher,

(It) an external adjusting knob supported by said enclosure andincluding a portion accessible for manual operation from outside saidenclosure,

(1') said cam shaft including a portion projecting through saidsupporting sleeve and into slidabie and non-rotatable engagement withsaid external adjusting knob, and

(j) said external adjusting knob being retained in position with respectto said enclosure by means independent of said cam shaft.

2. An electric control device comprising:

(a) an enclosure,

(5) a cam follower member pivotally supported in said enclosure,

(0) means operably connected to said cam follower member for varying thesensitivity of said device,

( d) said cam follower member having a generally linear cam followersurface,

(e) an elongated cam shaft,

( means supporting said cam shaft in said enclosure comprising agenerally tubular supporting sleeve, (g) said supporting sleeve beingrotatable to cause axial shifting of said cam shaft with respect to saidenclosure while said cam shaft is restrained from rotation with respectto said sleeve,

(11) a cam member carried adjacent one end of said shaft and disposedand arranged to engage said cam follower surface of said cam followermember,

(i) an adjusting member having at least a portion thereof accessible foroperation from outside said enclosure,

(j) said enclosure having indicia on the outer surface thereofcorresponding to different adjusted positions of said externallyaccessible adjusting member,

(k) said cam shaft including a portion projecting through saidsupporting sleeve and into slidable and non-rotatable engagement withsaid externally accessible adjusting member,

(I) said externally accessible adjusting member being movable to aposition corresponding to a particular indicia carried by said enclosureand retainable in said position while said supporting sleeve is rotatedto shift said cam shaft axially with relation to said enclosure to movesaid cam member linearly along said cam follower surface in a directionradially of said cam follower pivot to vary the mechanical advantage ofsaid cam member on said cam follower member without varying the rotativeposition of said cam shaft or said external adjusting member.

3. An electric control device comprising:

(a) a pivotally supported cam follower member,

(b) means operably connected to said cam follower member for varying thesensitivity of said device,

(c) an elongated cam shaft,

(d) a cam member carried by said cam shaft adjacent one end thereof anddisposed and arranged to engage said cam follower member,

(e) said cam follower member having a linear cam follower surfaceextending substantially radially of the pivot point of said cam followermember,

( )ha generally tubular supporting sleeve for said cam s aft,

(g) support means threadedly supporting said sleeve in said device, saidcam shaft being threadedly engaged in said supporting sleeve,

(h) manually engageable means for restraining said cam shaft fromrotation,

(i) means carried by said supporting sleeve for facilitating rotation ofsaid supporting sleeve while said cam shaft is restrained from rotation,

(i) said threaded engagement of said shaft in said sleeve being oppositein direction from said threaded engagement of said sleeve in itssupport, whereby said cam shaft moves with respect to said support 7means for said sleeve member at a rate determined by the sum of thepitches of the threads of said sleeve member and said cam shaft member,

(k) whereby to move said cam member substantially radially of saidpivoted cam member to vary the mechanical advantage of said cam memberon said cam follower memlber.

4. An electric control device comprising:

(a) a support,

([2) a cam follower member pivotally supported on said support, 1

() means operably connected to said cam follower member for varying thesensitivity of said device,

(d) said cam follower member including a linear cam follower surfaceextending in a direction generally radially of the pivot of said camfollower member,

(e) an elongated cam shaft,

(f) a generally tubular supporting sleeve threadedly carried by saidsupport,

(g) said cam shaft being threadedly received within said supportingsleeve,

(h) a cam member carried by said cam shaft adjacent one end thereof anddisposed and arranged to engage said cam follower surface of said camfollower member,

(i) said cam shaft including aportion projecting through said tubularsupporting sleeve and having its other end portion projecting beyondsaid tubular supporting sleeve and accessible for engagement to preventrotation of said cam shaft when desired,

(j) a rotation of said supporting sleeve while said cam shaft isrestrained from rotation serving to move said cam shaft axially withrespect to said support at a rate equal to the sum of the pitches of thethreads of said cam shaft and said tubular supporting and moving saidcam member along said cam follower surface radially of said pivot ofsaid cam follower member to vary the mechanical advantage of said cammember on said cam follower member.

5. An enclosed electric control device comprising:

(a) an enclosure, 7

(b) a cam follower memberpivotally supported in said enclosure, andincluding a linear cam follower sur- (,3 in face extending substantiallyradially from the pivot of said cam follower member, (0) means operablyconnected to sald cam follower member for varying the sensitivity ofsaid device,

(0!) an elongated threaded cam shaft in said enclosure,

(e) means supporting said cam shaft in said enclosure comprising agenerally tubular supporting sleeve threadedly supported with respect tosaid enclosure by means of external threads thereon,

(7) said cam shaft being threadedly engaged in the bore of saidsupporting sleeve,

(g) a cam member carried by said cam shaft adjacent one end thereof anddisposed and arranged to engage said cam follower surface of said camfollower (l)'and means carried by said supporting sleeve for Vfacilitating rotation of said supporting sleeve while said cam shaft isrestrained from rotation by means of said adjusting member, whereby toshift said cam shaft axially and tomove said cam member substantiallyradially of said pivot of said cam follower member to vary themechanical advantage of,"

said cam member on said cam follower member while said adjusting memberis retained in a predetermined position with respect to said externalindicia on said enclosure.

6. An electric control device as set forth in claim 5 wherein saiddevice also comprises:

(a) an electromagnetic armature movable to initiate actuation of saiddevice, and

(b) a tension spring having one end operably connected to said armatureand having ther other end operably connected to said cam follower memberwhereby variation in the rotated position of said cam follower membercauses variation in the tension of said spring.

References Cited by the Examiner UNITED STATES PATENTS 3,084,236 4/63Klein et al.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

1. AN ELECTRIC CONTROL DEVICE INCLUDING: (A) AN ENCLOSURE, (B) A CAMFOLLOWER MEMBER PIVOTALLY SUPPORTED IN SAID ENCLOSURE AND INCLUDING ACAM FOLLOWER SURFACE, (C) MEANS OPERABLY CONNECTED TO SAID CAM FOLLOWERMEMBER FOR VARYING THE SENSITIVITY OF SAID DEVICE, (D) AN ELONGATED CAMSHAFT, (E) A GENERALLY TUBULAR SUPPORTING SLEEVE SUPPORTING SAID CAMSHAFT IN SAID CLOSURE, (F) SAID SUPPORTING SLEEVE BEING ROTATABLE WHILESAID CAM SHAFT IS RESTRAINED FROM ROTATION TO CAUSE LONGITUDINALSHIFTING OF SAID SHAFT WITH RESPECT TO SAID ENCLOSURE, ( G) A CAM MEMBERCARRIED BY SAID CAM SHAFT ADJACENT ONE END THEREOF AND DISPOSED ANDARRANGED TO ENGAGE SAID CAM FOLLOWER SURFACE OF SAID CAM FOLLOWERMEMBER, (H) AN EXTERNAL ADJUSTING KNOB SUPPORTED BY SAID ENCLOSURE ANDINCLUDING A PORTION ACCESSIBLE FOR MANUAL OPERATION FROM OUTSIDE SAIDENCLOSURE, (I) SAID CAM SHAFT INCLUDING A PORTION PROJECTING THROUGHSAID SUPPORTING SLEEVE AND INTO SLIDABLE AND NON-ROTATABLE ENGAGEMENTWITH SAID EXTERNAL ADJUSTING KNOB, AND (J) SAID EXTERNAL ADJUSTING KNOBBEING RETAINED IN POSITION WITH RESPECT TO SAID ENCLOSURE BY MEANSINDEPENDENT OF SAID CAM SHAFT.